import AppKit
import Combine
import SwiftUI

/// Manages the full-screen overlay NSPanel for each display with
/// interactive gesture-driven transitions.
@MainActor
final class OverlayWindowController {
    // MARK: - State

    private enum State {
        case idle
        case tracking        // gesture active, panels visible, driving progress
        case committing      // spring animating to 1.0
        case shown           // fully visible and interactive
        case dismissTracking // gesture active while shown, driving progress down
        case dismissing      // spring animating to 0.0 (committed dismiss)
        case cancelling      // spring animating back (cancel gesture)
    }

    private var state: State = .idle
    private var panels: [NSPanel] = []
    private var layoutEngines: [ScreenKey: LayoutEngine] = [:]
    private let gestureProgress: GestureProgress
    private var springAnimator: SpringAnimator?
    private var captureGeneration: Int = 0

    /// Cached thumbnails from previous activation, keyed by window ID.
    private var thumbnailCache: [CGWindowID: CGImage] = [:]

    /// Floating window that follows the cursor during cross-monitor drag.
    private var dragFloatingWindow: NSWindow?
    private var dragObservation: AnyCancellable?

    var onWindowSelected: ((WindowInfo) -> Void)?
    var onDismiss: (() -> Void)?

    // Normalization: 10% of trackpad range = full reveal
    private let normalizationDivisor: Float = 0.10

    // Commit thresholds
    private let commitProgressThreshold: CGFloat = 0.3
    private let commitVelocityThreshold: Float = 0.2

    var isVisible: Bool {
        switch state {
        case .idle: return false
        default: return true
        }
    }

    init(gestureProgress: GestureProgress) {
        self.gestureProgress = gestureProgress
        startObservingDrag()
    }

    // MARK: - Gesture callbacks

    func gestureDidBegin() {
        mctLog("[MCT] gestureDidBegin state=%d", state == .idle ? 0 : state == .shown ? 1 : 2)
        switch state {
        case .idle, .cancelling, .dismissing:
            // Interrupt any running animation and start fresh
            springAnimator?.stop()
            springAnimator = nil

            // If panels exist from a cancelling/dismissing animation, remove them
            if state != .idle {
                removePanels()
                gestureProgress.thumbnailsReady = false
                gestureProgress.layouts.removeAll()
            }

            state = .tracking
            captureGeneration += 1
            let gen = captureGeneration

            createPanels(interactive: false)
            setProgress(0.0, phase: .tracking)

            // Phase 1: enumerate + apply cached thumbnails immediately
            var windows = WindowEnumerator.enumerateWindows()
            applyCachedThumbnails(to: &windows)
            applyThumbnails(windows: windows)

            // Phase 2: capture fresh thumbnails in background
            Task {
                var freshWindows = windows
                await ThumbnailCapture.captureThumbnails(for: &freshWindows)
                let captured = freshWindows
                await MainActor.run {
                    guard gen == self.captureGeneration else { return }
                    self.updateThumbnailCache(from: captured)
                    self.applyThumbnails(windows: captured)
                }
            }

        case .shown, .committing:
            // Begin dismiss tracking (interrupt commit animation if mid-spring)
            springAnimator?.stop()
            springAnimator = nil
            state = .dismissTracking
            setInteractive(false)
            setProgress(gestureProgress.progress, phase: .dismissTracking)

        case .tracking, .dismissTracking:
            // Already tracking — ignore duplicate began
            break
        }
    }

    func gestureDidChange(rawDY: Float, rawVelocity: Float) {
        switch state {
        case .tracking:
            let normalized = CGFloat(clamp(rawDY / normalizationDivisor, min: 0, max: 1))
            setProgress(normalized, phase: .tracking)

        case .dismissTracking:
            // Negative DY (swipe down) drives dismiss; positive re-opens
            let normalized = CGFloat(clamp(-rawDY / normalizationDivisor, min: 0, max: 1))
            let progress = 1.0 - normalized
            setProgress(progress, phase: .dismissTracking)

        default:
            break
        }
    }

    func gestureDidEnd(rawDY: Float, rawVelocity: Float) {
        switch state {
        case .tracking:
            let normalized = CGFloat(clamp(rawDY / normalizationDivisor, min: 0, max: 1))
            let shouldCommit = normalized > commitProgressThreshold || rawVelocity > commitVelocityThreshold
            if shouldCommit {
                animateToCommit(from: normalized, velocity: CGFloat(rawVelocity))
            } else {
                animateToCancel(from: normalized, velocity: CGFloat(rawVelocity))
            }

        case .dismissTracking:
            let dismissNormalized = CGFloat(clamp(-rawDY / normalizationDivisor, min: 0, max: 1))
            let currentProgress = 1.0 - dismissNormalized
            let shouldDismiss = dismissNormalized > commitProgressThreshold || (-rawVelocity) > commitVelocityThreshold
            if shouldDismiss {
                animateToDismiss(from: currentProgress, velocity: CGFloat(rawVelocity))
            } else {
                animateToCancelDismiss(from: currentProgress, velocity: CGFloat(rawVelocity))
            }

        default:
            break
        }
    }

    func gestureDidCancel() {
        switch state {
        case .tracking:
            let current = gestureProgress.progress
            animateToCancel(from: current, velocity: 0)

        case .dismissTracking:
            let current = gestureProgress.progress
            animateToCancelDismiss(from: current, velocity: 0)

        default:
            break
        }
    }

    // MARK: - Hotkey toggle

    func toggle() {
        mctLog("[MCT] toggle called, state=%d", state == .idle ? 0 : 1)
        switch state {
        case .idle:
            // Hotkey show: create panels, animate to fully shown
            state = .committing
            springAnimator?.stop()
            springAnimator = nil
            captureGeneration += 1
            let gen = captureGeneration

            createPanels(interactive: true)
            setProgress(0.0, phase: .committing)

            NSApp.activate(ignoringOtherApps: true)
            if let firstPanel = panels.first {
                firstPanel.makeKey()
            }

            // Phase 1: enumerate + apply cached thumbnails immediately
            let t0 = CFAbsoluteTimeGetCurrent()
            var windows = WindowEnumerator.enumerateWindows()
            applyCachedThumbnails(to: &windows)
            applyThumbnails(windows: windows)
            let t1 = CFAbsoluteTimeGetCurrent()
            mctLog("[MCT] phase1 (cached): %.0f ms (%d windows)", (t1 - t0) * 1000, windows.count)

            // Phase 2: capture fresh thumbnails in background and swap in
            Task {
                var freshWindows = windows
                await ThumbnailCapture.captureThumbnails(for: &freshWindows)
                let t2 = CFAbsoluteTimeGetCurrent()
                mctLog("[MCT] phase2 (capture): %.0f ms", (t2 - t1) * 1000)

                let captured = freshWindows
                await MainActor.run {
                    guard gen == self.captureGeneration else { return }
                    self.updateThumbnailCache(from: captured)
                    self.applyThumbnails(windows: captured)
                }
            }

            animateToCommit(from: 0, velocity: 0, stiffness: 800.0)

        case .shown:
            animateToDismiss(from: 1.0, velocity: 0, stiffness: 800.0)

        case .committing:
            // Reverse: dismiss from current progress
            let current = gestureProgress.progress
            animateToDismiss(from: current, velocity: 0, stiffness: 800.0)

        case .dismissing, .cancelling:
            // Reverse: reopen from current progress
            let current = gestureProgress.progress
            setInteractive(true)
            NSApp.activate(ignoringOtherApps: true)
            if let firstPanel = panels.first {
                firstPanel.makeKey()
            }
            animateToCommit(from: current, velocity: 0, stiffness: 800.0)

        default:
            let current = gestureProgress.progress
            animateToDismiss(from: current, velocity: 0, stiffness: 800.0)
        }
    }

    /// Dismiss from external trigger (Escape key, background tap).
    func dismiss() {
        switch state {
        case .shown:
            animateToDismiss(from: 1.0, velocity: 0, stiffness: 800.0)
        case .idle:
            break
        default:
            let current = gestureProgress.progress
            animateToDismiss(from: current, velocity: 0, stiffness: 800.0)
        }
    }

    // MARK: - Spring animations

    private func animateToCommit(from current: CGFloat, velocity: CGFloat, stiffness: CGFloat = 300.0) {
        state = .committing
        gestureProgress.phase = .committing
        springAnimator?.stop()
        springAnimator = SpringAnimator(
            from: current,
            to: 1.0,
            initialVelocity: velocity,
            stiffness: stiffness,
            onUpdate: { [weak self] value in
                self?.gestureProgress.progress = value
            },
            onComplete: { [weak self] in
                self?.commitComplete()
            }
        )
        springAnimator?.start()
    }

    private func animateToCancel(from current: CGFloat, velocity: CGFloat) {
        state = .cancelling
        gestureProgress.phase = .cancelling
        springAnimator?.stop()
        springAnimator = SpringAnimator(
            from: current,
            to: 0.0,
            initialVelocity: velocity,
            onUpdate: { [weak self] value in
                self?.gestureProgress.progress = value
            },
            onComplete: { [weak self] in
                self?.cancelComplete()
            }
        )
        springAnimator?.start()
    }

    private func animateToDismiss(from current: CGFloat, velocity: CGFloat, stiffness: CGFloat = 300.0) {
        state = .dismissing
        gestureProgress.phase = .dismissing
        springAnimator?.stop()
        springAnimator = SpringAnimator(
            from: current,
            to: 0.0,
            initialVelocity: velocity,
            stiffness: stiffness,
            onUpdate: { [weak self] value in
                self?.gestureProgress.progress = value
            },
            onComplete: { [weak self] in
                self?.dismissComplete()
            }
        )
        springAnimator?.start()
    }

    private func animateToCancelDismiss(from current: CGFloat, velocity: CGFloat) {
        // Animate back to fully shown
        state = .committing
        gestureProgress.phase = .committing
        springAnimator?.stop()
        springAnimator = SpringAnimator(
            from: current,
            to: 1.0,
            initialVelocity: velocity,
            onUpdate: { [weak self] value in
                self?.gestureProgress.progress = value
            },
            onComplete: { [weak self] in
                self?.commitComplete()
            }
        )
        springAnimator?.start()
    }

    // MARK: - Completion handlers

    private func commitComplete() {
        state = .shown
        gestureProgress.progress = 1.0
        gestureProgress.phase = .committed
        setInteractive(true)

        NSApp.activate(ignoringOtherApps: true)
        if let firstPanel = panels.first {
            firstPanel.makeKey()
        }
    }

    private func cancelComplete() {
        state = .idle
        gestureProgress.progress = 0.0
        gestureProgress.phase = .idle
        gestureProgress.thumbnailsReady = false
        gestureProgress.layouts.removeAll()
        gestureProgress.dragState = nil
        layoutEngines.values.forEach { $0.invalidate() }
        layoutEngines.removeAll()
        removeDragFloatingWindow()
        removePanels()
    }

    private func dismissComplete() {
        state = .idle
        gestureProgress.progress = 0.0
        gestureProgress.phase = .idle
        gestureProgress.thumbnailsReady = false
        gestureProgress.layouts.removeAll()
        gestureProgress.dragState = nil
        layoutEngines.values.forEach { $0.invalidate() }
        layoutEngines.removeAll()
        removeDragFloatingWindow()
        onDismiss?()
        removePanels()
    }

    // MARK: - Panel lifecycle

    private func createPanels(interactive: Bool) {
        removePanels()

        for screen in NSScreen.screens {
            let panel = createPanel(for: screen)
            panel.ignoresMouseEvents = !interactive
            panel.alphaValue = 1.0

            let overlayView = OverlayView(
                gestureProgress: gestureProgress,
                screenBounds: screen.frame,
                onSelect: { [weak self] windowInfo in
                    self?.selectWindow(windowInfo)
                },
                onDismiss: { [weak self] in
                    self?.dismiss()
                },
                onDrop: { [weak self] point in
                    self?.handleDrop(at: point)
                }
            )

            panel.contentView = NSHostingView(rootView: overlayView)
            panel.makeKeyAndOrderFront(nil)
            panel.orderFrontRegardless()

            panels.append(panel)
        }
    }

    private func removePanels() {
        for panel in panels {
            panel.orderOut(nil)
        }
        panels.removeAll()
    }

    private func setInteractive(_ interactive: Bool) {
        for panel in panels {
            panel.ignoresMouseEvents = !interactive
        }
    }

    private func createPanel(for screen: NSScreen) -> NSPanel {
        let panel = OverlayPanel(
            contentRect: screen.frame,
            styleMask: [.borderless, .nonactivatingPanel],
            backing: .buffered,
            defer: false
        )
        panel.isFloatingPanel = true
        panel.level = .screenSaver
        panel.collectionBehavior = [.canJoinAllSpaces, .fullScreenAuxiliary]
        panel.isOpaque = false
        panel.backgroundColor = .clear
        panel.hasShadow = false
        panel.hidesOnDeactivate = false
        panel.acceptsMouseMovedEvents = true
        panel.ignoresMouseEvents = false
        return panel
    }

    // MARK: - Cross-monitor drag

    func startObservingDrag() {
        dragObservation = gestureProgress.$dragState
            .receive(on: RunLoop.main)
            .sink { [weak self] state in
                guard let self else { return }
                if let state = state {
                    if self.dragFloatingWindow == nil {
                        self.createDragFloatingWindow(for: state)
                    }
                    self.updateDragFloatingWindow(position: state.currentScreenPosition)
                } else {
                    self.removeDragFloatingWindow()
                }
            }
    }

    private func createDragFloatingWindow(for state: DragState) {
        let windowInfo = state.windowInfo

        // Size: 200px wide, aspect-preserved
        let aspect = windowInfo.frame.height / max(windowInfo.frame.width, 1)
        let thumbWidth: CGFloat = 200
        let thumbHeight = thumbWidth * aspect

        let window = NSWindow(
            contentRect: NSRect(x: 0, y: 0, width: thumbWidth, height: thumbHeight),
            styleMask: [.borderless],
            backing: .buffered,
            defer: false
        )
        window.level = NSWindow.Level(Int(CGWindowLevelForKey(.screenSaverWindow)) + 1)
        window.isOpaque = false
        window.backgroundColor = .clear
        window.hasShadow = true
        window.ignoresMouseEvents = true
        window.collectionBehavior = [.canJoinAllSpaces]

        if let thumb = windowInfo.thumbnail {
            let nsImage = NSImage(cgImage: thumb, size: NSSize(width: thumbWidth, height: thumbHeight))
            let imageView = NSImageView(frame: NSRect(x: 0, y: 0, width: thumbWidth, height: thumbHeight))
            imageView.image = nsImage
            imageView.imageScaling = .scaleProportionallyUpOrDown
            imageView.wantsLayer = true
            imageView.layer?.cornerRadius = 8
            imageView.layer?.masksToBounds = true
            imageView.layer?.opacity = 0.85
            window.contentView = imageView
        }

        window.alphaValue = 0.9
        window.orderFrontRegardless()
        dragFloatingWindow = window
    }

    private func updateDragFloatingWindow(position: CGPoint) {
        guard let window = dragFloatingWindow else { return }
        let size = window.frame.size
        // Center the floating window on the cursor
        window.setFrameOrigin(NSPoint(x: position.x - size.width / 2,
                                       y: position.y - size.height / 2))
    }

    private func removeDragFloatingWindow() {
        dragFloatingWindow?.orderOut(nil)
        dragFloatingWindow = nil
    }

    private func handleDrop(at point: CGPoint) {
        guard let dragState = gestureProgress.dragState else { return }
        let windowInfo = dragState.windowInfo

        // Find which screen the cursor landed on
        let targetScreen = NSScreen.screens.first(where: { $0.frame.contains(point) })
            ?? NSScreen.screens.first!
        let primaryHeight = NSScreen.screens.first?.frame.height ?? 0

        // Center the window on the target screen (Quartz coords: top-left origin)
        let targetQuartz = quartzFrame(for: targetScreen, primaryHeight: primaryHeight)
        let winW = windowInfo.frame.width
        let winH = windowInfo.frame.height
        let dropPoint = CGPoint(
            x: targetQuartz.midX - winW / 2,
            y: targetQuartz.midY - winH / 2
        )

        // Move the window
        _ = AccessibilityBridge.moveWindow(pid: windowInfo.pid, windowID: windowInfo.windowID, to: dropPoint)

        // Clear drag state
        gestureProgress.dragState = nil
        removeDragFloatingWindow()

        // Invalidate layout engines so both source and target screens recompute fresh grids
        let sourceKey = dragState.sourceScreenKey
        let targetKey = ScreenKey(targetScreen.frame)
        layoutEngines[sourceKey]?.invalidate()
        layoutEngines[targetKey]?.invalidate()

        // Re-enumerate and patch the moved window's frame immediately,
        // since CGWindowList may not yet reflect the AX position change.
        captureGeneration += 1
        let gen = captureGeneration
        var windows = WindowEnumerator.enumerateWindows()
        applyCachedThumbnails(to: &windows)
        let newFrame = CGRect(origin: dropPoint, size: windowInfo.frame.size)
        for i in windows.indices where windows[i].windowID == windowInfo.windowID {
            windows[i] = WindowInfo(
                windowID: windows[i].windowID,
                title: windows[i].title,
                appName: windows[i].appName,
                appBundleID: windows[i].appBundleID,
                appIcon: windows[i].appIcon,
                frame: newFrame,
                pid: windows[i].pid,
                isOnScreen: windows[i].isOnScreen,
                thumbnail: windows[i].thumbnail
            )
        }
        applyThumbnails(windows: windows)

        // Re-order panels to front so they aren't hidden behind each other
        for panel in panels {
            panel.orderFrontRegardless()
        }

        // Background: re-enumerate with fresh system data + thumbnails
        Task {
            try? await Task.sleep(nanoseconds: 200_000_000) // 200ms for AX move to propagate
            guard gen == self.captureGeneration else { return }
            var freshWindows = WindowEnumerator.enumerateWindows()
            self.applyCachedThumbnails(to: &freshWindows)
            await ThumbnailCapture.captureThumbnails(for: &freshWindows)
            let captured = freshWindows
            await MainActor.run {
                guard gen == self.captureGeneration else { return }
                self.updateThumbnailCache(from: captured)
                self.applyThumbnails(windows: captured)
            }
        }
    }

    // MARK: - Helpers

    private func setProgress(_ value: CGFloat, phase: GesturePhase) {
        gestureProgress.progress = value
        gestureProgress.phase = phase
    }

    private func applyThumbnails(windows: [WindowInfo]) {
        let screens = NSScreen.screens
        let primaryHeight = screens.first?.frame.height ?? 0

        var layouts: [ScreenKey: LayoutResult] = [:]
        for screen in screens {
            let key = ScreenKey(screen.frame)

            // Convert screen frame from AppKit coords (bottom-left origin) to
            // Quartz coords (top-left origin) to match WindowInfo.frame
            let qFrame = quartzFrame(for: screen, primaryHeight: primaryHeight)

            // Only include windows whose center falls on this screen
            let screenWindows = windows.filter { window in
                let center = CGPoint(x: window.frame.midX, y: window.frame.midY)
                return qFrame.contains(center)
            }

            let groups = WindowEnumerator.groupWindows(screenWindows)
            let snapshot = WindowSnapshot(groups: groups)

            if layoutEngines[key] == nil {
                layoutEngines[key] = LayoutEngine()
            }
            let layout = layoutEngines[key]!.layout(snapshot: snapshot, screenBounds: screen.frame)
            layouts[key] = layout
        }

        gestureProgress.layouts = layouts
        gestureProgress.thumbnailsReady = true
        gestureProgress.thumbnailGeneration += 1
    }

    /// Apply cached thumbnails to windows that have a cache hit.
    private func applyCachedThumbnails(to windows: inout [WindowInfo]) {
        for i in windows.indices {
            if let cached = thumbnailCache[windows[i].windowID] {
                windows[i].thumbnail = cached
            }
        }
    }

    /// Update the thumbnail cache from freshly captured windows.
    private func updateThumbnailCache(from windows: [WindowInfo]) {
        for window in windows {
            if let thumb = window.thumbnail {
                thumbnailCache[window.windowID] = thumb
            }
        }
        // Prune stale entries for windows that no longer exist
        let currentIDs = Set(windows.map { $0.windowID })
        for key in thumbnailCache.keys where !currentIDs.contains(key) {
            thumbnailCache.removeValue(forKey: key)
        }
    }

    /// Convert an NSScreen frame (AppKit bottom-left origin) to Quartz display
    /// coordinates (top-left origin) so we can compare with WindowInfo.frame.
    private func quartzFrame(for screen: NSScreen, primaryHeight: CGFloat) -> CGRect {
        let f = screen.frame
        return CGRect(x: f.origin.x,
                      y: primaryHeight - f.origin.y - f.height,
                      width: f.width,
                      height: f.height)
    }

    private func selectWindow(_ windowInfo: WindowInfo) {
        dismiss()
        onWindowSelected?(windowInfo)
        _ = AccessibilityBridge.activateWindow(pid: windowInfo.pid, windowID: windowInfo.windowID)
    }

    private func clamp(_ value: Float, min minVal: Float, max maxVal: Float) -> Float {
        Swift.min(Swift.max(value, minVal), maxVal)
    }
}

// MARK: - Custom Panel

private final class OverlayPanel: NSPanel {
    override var canBecomeKey: Bool { true }
    override var canBecomeMain: Bool { true }
}